Obsessive-Compulsive Disorder: Phenomenology, Pathophysiology, and TreatmentObsessive compulsive disorder affects approximately one person in 40 and causes great suffering. Effective treatments are available that can help many, and our understanding of the psychology, neurobiology, and clinical treatment of the disorder has advanced dramatically over the past 25 years. Nevertheless, much remains to be learned, and a substantial minority of patients benefit little even from the best treatments we have to offer today. This